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Medical Forum / General / Laboratory / October 2003coagulation stability studies
does anyone have any stability studies for protime/ptt testing. other than the nccls recommended times?? we are interested in expanding the 4 hour limit for ptt testing on non-heparinized patients -- > does anyone have any stability studies for protime/ptt testing. other > than the nccls recommended times?? we are interested in expanding the > 4 hour limit for ptt testing on non-heparinized patients Well....... All the "experts" say four hours, but two years ago at the DAWN user's symposium (yawn!) some chap from Aberdeen reckoned their sample deliveries were such that coag samples were regularly over a day old on testing, and that it made no difference to the result. MB Your suspicions are right on! The studies I did, about three years ago, showed a stability out to at least 6-8 hours. This has been discussed before. As far as practical coag. is concerned the NCCLs recommendations are not "total inclusive", when one is talking PT, but are probably more applicable to PTT. I will have to check to see how dated the NCCLs reference and on whom they relied. I am rather busy this week, so it might be a week before I get to looking at them. You don't have to use other studies, or even take my rather profound statements, do your own, keep the data and use it. Just write your procedures / criteria with that data as a reference. > does anyone have any stability studies for protime/ptt testing. other > than the nccls recommended times?? we are interested in expanding the > 4 hour limit for ptt testing on non-heparinized patients > > -- The reference NCCLS sites in their most recent publication (1998) is: Adcock DM, Kressin DC, Marlar RA. "The effects of time and temperature variables on routine coagulation testing. Blood Collection and Fibrinolysis. In press" no date When I did our local studies, I was more interested in the PT and heparinized PTT. In unheparinized patients I have noted a rather fast drop off in _PTT_ stability after 4 hours. Then again, if it is in still in the normal range will it matter? > Your suspicions are right on! > The studies I did, about three years ago, showed a stability out to at least [quoted text clipped - 11 lines] > > > > -- > does anyone have any stability studies for protime/ptt testing. Many moon ago, the lab I worked in took on coag tests drawn at Dr.s offices in the area. We ran an internal study to find out the stability for ourselves. The PTs were stable for at least 12 hours, the PTTs for four, IIRC. Pete, MT(ASCP). I brought this question up about a year ago. Anyone note a longer PTT for pediatrics patients. I sometimes wonder if the PTT range is different in these patients since most of the ones I see are sick and might be on antibiotics (here is a concern over vitamin K depletion real or speculated??). I seem to note a significant number of pediatric patients in our upper normal range, or just above. I used n = 50, this year, for our PTT normal range, but of course it lacks healthy pediatric patients. I believe the consensus here last year was that the ranges are the same. If so back to the question for the group noticing many peds patients in your upper normal range? Thanks > > does anyone have any stability studies for protime/ptt testing. > [quoted text clipped - 4 lines] > > Pete, MT(ASCP). |
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